Limit switch actuator



July 13, 1965 M. B. HALL LIMIT SWITCH ACTUATOR Original Filed Nov. 29.1960 v law 998mm;

United States Patent 3,194,964 LlMiT SWETCH ACT JATGR Marchand BlanchardHali, Ulyrnpia Fields, 1il., assignor g lzrterlake Steel Corporation, aeorperation of New (Briginal application Nov. 2Q, 1966, Ser. No. 72,409,new Patent No. 3,652,178, dated Sept. 4, 1962. Divided and thisapplication Aug. 31, 1962, Ser. No. 226,833

5 Claims. (Cl. 260-47) This application is a division of my co-pendingapplication Serial No. 72,409, filed November 29, 1960, now LettersPatent 3,052,178, issued September 4, 1962.

This invention relates to the art of motor control means andparticularly to control means for the actuation of an electric motor inresponse to the rotation of a shaft rotated by said motor.

In my co-pending application there is shown a retractable binder strapguide which is extended and retracted by power means between a strapreceiving position and a position clear of the strap path. The powermeans shown is an electric motor. The extreme extended and retractedpositions of the strap guide are accurately determined by arresting themotor rotation as one or the other of the two electric switches areactuated. The electric switches are positioned with their actuating armsin the path of stops provided on a shaft driven by the motor in such away that the stops cause actuation of the switches to control the motoractuation in response to the amount of rotation of the shaft.

Although applied in my co-pending application to control of aretractable binder strap guide which is powered by an electric motor,the invention of this application has a broader utility because it canbe applied to any device having a rotatable shaft powered by an electricmotor. It is, therefore, the principal object of this invention toprovide a control means for controlling the rotation of a shaft drivenby an electric motor wherein a threaded portion of the shaft is engagedwith a threaded switch carrier so that rotation of the shaft by theelectric motor causes the switch carrier to move longitudinally alongthe shaft between two spaced adjustable stops provided on the shaft,thus causing the arms of two switches mounted on the switch carrier tobe alternately actuated by contact or separation from the two stops tocontrol the actuation of the motor and thereby control rotation of theshaft.

It is believed that such a device can have wide application on lengthmeasuring devices wherein closer accuracy is required. For example, itis common to have devices which measure out predetermined lengths ofstrip material and cut them to length. The accuracy of such devices isoften unsatisfactory. It is another object of this invention to providea motor control device which is readily adaptable for application on alength measuring device whereby very accurate lengths can be measuredand cut. It is necessary only to adapt the control means to a rotatingshaft which can be, for example, a shaft for a feed wheel used to propelthe strip material forward.

It is another object of the invention to provide such an improved devicehaving easy adjustability so that the length of strip feed time or therotation time of the control shaft can be varied expeditiously asnecessary.

Other objects and advantages of the invention should become apparentupon reference to the accompanying drawings in which FIG. 1 shows a topplan view of the control means of the invention;

FIG. 2 shows a front elevation of the control means of the invention;

FIG. 3 shows a right end view of the control means as viewed in FIG. 1;

FIG. 4 shows an enlarged sectional view of certain portions of thecontrol means for illustrative purposes; and

FIG. 5 shows a simplified schematic wiring diagram of the electriccontrol circuit used with the control means of FIGS. 1 to 4.

As shown in FIGS. 1, 2 and 3, a housing 18 is provided which is ajournal housing for a shaft 22 connected to be driven by an electricmotor 59. For purposes of this invention, the housing 18 could actuallybe the electric motor which drives the shaft 22 directly. As shown, thehousing 18 is the journal housing for the shaft 22 and also can containthe motor 59 as well as any conventional speed changing drive betweenthe motor 5% and the shaft 22.

The end of shaft 22 which passes through bearing 26 is threaded andprojects quite far beyond the housing 18 in which the bearing 26 ismounted. This threaded end 22a of the shaft 22 is first provided withtwo threaded nuts 60 and 61 which can be locked together in a fixedposition on the shaft 22 by means of two lock washers 62. The nut 61 isprovided internally with the inner end of a helical spring 63 which iswelded or soldered to it. The spring 63 acts as the threads of the nut61 and engages the threads on the end 22a of the shaft 22. The nut 60 isinternally threaded to directly engage the threads of the shaft end 22a.With the spring 63 securely bonded to the nut 61 as described, rotationof the nut 61 on the threads of the shaft end 22a causes rotation of thespring 63 with it. Beyond the free end 63a of the spring 63 is mountedan inverted U-shaped bracket 64 by means of an internally threadedcircular nut 65. The circular nut 65 has an enlarged center portionhaving annular end walls 65a guided against the inside walls of thebracket 64 and it also has reduced diameter ends 65b and 65c whichproject into round openings 66 and 67 in the side walls of the bracket64. Through apertures in the side walls of the bracket 64 is alsomounted a screw 68 which is held in place by means of a nut 69 at itsend. The effect of tightening of the nut 69 on the screw 68 is to drawthe two side walls of the bracket 64 together and thereby clamp thecircular nut 65 fixed relative to the bracket 64. When rotation of thecircular nut 65 is required for adjustment, the nut 65 is loosened sothat the pressure of the side plates of the bracket 64 is relievedagainst the ends of the circular nut 65, at which time the circular nutis free to be rotated relative to the bracket 64. During this rotationalmovement, it is urged one way or another on the shaft 22 because of itsthreaded engagement with it. The purpose of this adjustment of thecircular nut 65 is hereinafter described.

Adjacent to the extreme end of the shaft end 22a are two more nuts 70and 71. The nut 71 is similar to 6d and is internally threaded todirectly engage the threads of the shaft 22 and it is a locking nut fornut '76. The nut 70 is similar to nut 61 and is provided with a helicalspring 72 which is soldered or welded to it in the same manner. Thespring 72 acts as the internal thread for the nut 70 on the threads ofthe shaft 22. Rotation of the nut 70 causes rotation of the spring 72and causes the spring to move one way or the other longitudinally on theshaft, depending upon which direction the nut is rotated.

On the outer surfaces of the side walls of the bracket 64 are mountedtWo switches 73 and 74. These switches have actuating arms 73a and 74awhich extend transversely over the shaft 22. These switches 73 and 74are secured by means of screws '75 to the side walls of the bracket 64.The bracket 64 is provided with a pin 76 which has its inner end securedto the housing 18 while its outer end is secured through the side wallsof the bracket 64. This pin maintains the bracket 64 in a fixed angularrelationship to the shaft 22.

' they would be initially.

laterally across the shaft 22 in the path of the springs 63 and 72, asthe bracket 64 is moved along the shaft 22 in one direction or another,the arms 73a and 74a are actuated alternately by contact with the ends63a and 72a of the two springs.

In actual operation, the switches are used to arrest the operation ofthe driving motor59. in either direction of rotation of the shaft 22. InFIG. 1, it may be assumed that the positions of the switch arms 73a and74a are as In this case the arm 74a is pivoted upwardly onto the springend 72a. In this position of the arm 74a, the contacts of switch 74- areopen. At this same time, the arm 73a is off of the spring end 63a andresting upon the threads of the shaft 22. In this position of the arm73a, the contacts of the switch 73 are closed. When it is desired torotate the shaft 22-, another switch in series with switch 73 is closedand this energizes the motor 59 to cause rotation of the shaft 22 in onedirection. As the shaft 22 is rotated in a first direction, its threadedengagement with the circular nut 65 causes the bracket 64 to be movedtoward the left as viewed in FIG. 1. Movement of thebracket 64 to theleft causes the switches 73 and 74 to likewise be moved to the leftrelative to the shaft 22 so that the switch arm 74a falls off of the end72a of the spring and onto the threaded portions of the shaft 22 toclose the contacts of the switch 74. Shortly thereafter, when thebracket 64 has moved far enough, the switch arm 7.3a contacts the end63a of the spring 63 to cause the arm 73a to be raised to open thecontacts of the switch 73. Closing of the contacts of switch 74 preparesthe circuit for later initiating reverse rotation of the shaft 22, whileopening of the contacts of switch 73 breaks the circuit with theelectric I motor 59 and thereby arrests its operation to arrest therotation of the shaft 22. In this manner, by having the springs 63 and72 properly spaced, it is possible to accurately determine the number ofrevolutions made before rotation of the shaft 22 stops. 7

The fit of the pin 76 through the walls of the bracket 64 is looseenough that the bracket 64 is free to move over it as the shaft 22 isrotated to cause such movement. FIG. 4 indicates schematically thereason for the adjustment of the circular nut 65 relative to the bracket64. If the initial angular position of where the start'of the internalthread of the circular nut is not proper, it is possible that the switcharm 74a will possibly first contact the end 72a of the spring '72 at aposition indicated by phantom lines in that view. In that position it ispossible that insuflicient movement of the switch arm 74a will not haveoccurred to completely actuate the switch. If this is true, the nut 69is loosened and the circular nut 65 is adjusted until arm 74a is uponthe spring end 72a as shown in solid outline in FIG. 4.

By referring to FIG. 5, the entire electrical operation of the controlsinvolving switches 73- and 74 can be described. In FIG. 5, a suitablesupply voltage is applied between wires 77 and 78. Upon closing of amaster switch 79 connected to these wires 77' and 78, the voltage iscarried between conducters 80 and 81. At this time. none of theelectrical components are energized. However, switch 73 is closedbecause its switch arm 73a is ofi of the end 63a of the spring 63 andswitch 74- is open be cause its arm 74a is on the spring end 72a. Inorder to cause the shaft 22 to be rotated in said first direction by themotor 59, the switch 82 is closed manually. This applies voltage fromconductors 80 and 81 across a relay solenoid 83 by way of closed switch73. Thi energizes solenoid 83 to cause the solenoid contact switches 83aand 8311 to be closed. Closing of contact switch 83b maintains solenoid83 energized after the switch 82 is spring returned after release by theoperator. Contact switch 83a energizes the electric motorthroughconductors 84 and 85 so that the motor 59 rotates in said firstdirection. As rotation of the shaft 22 continues, the bracket 64 ismoved to the left, as viewed in FIG. 1. The movement of the bracket 64;correspondingly moves the switches 73 and 74 to the left with it. At apredetermined time, determined by the spacing between the spring ends63a and 72a, the switch arm 73a rides up on to the spring end 63a tocause switch 73 to be opened. During the initial movement of the bracket64, however, switch 74:: is closed as the spring arm 74:; falls off ofthe spring end 72a. Opening of switch 73 de-energizes relay solenoid $3to allow the spring return of its contact switches 83a and 83b to open.CpClliIlg of switch contact 83b ets up the circuit for the next cycle ofoperation while opening of switch contact 83a tie-energizes the motor 59and arrests its motion and likewise the rotation of shaft 22.

When it is desired to reverse rotation of the shaft 22, a switch 36 isclosed manually to energize a relay solenoid 37 through the closedswitch 74. Energization of the solenoid 37 causes its switch contacts87a and 87b to be closed. 37b is a holding contact for solenoid 87 tomaintain it energized after the actuating button for the switch 86 isspring returned upon manual release. Closing of switch contact 87aenergizes the motor 59 through conductors 83 and 85. Since the motor 59is a reversing type motor wherein its direction of rotation isdetermined by whether it is energized through conductors 8 or 33,energizing this motor 59 through the conductor 88 causes it to berotated in a direction to cause reverse rotation of the shaft 22. Whenthe shaft 22 rotates sufficiently, the bracket 64 will have movedsufficiently to the right that the switch arm 73a will have moved off ofthe spring end 63a to close switch 73 and the switch arm 740 will havemoved onto the spring end 72a so that the switch 74 is again opened. Theparts are then all in the positions as shown in FIGS. 1 and 2 inreadiness for the cycle to be repeated.

Although only a single embodiment of the invention has been shown anddescribed, it should be understood that the invention can be made inmany different ways without departing from the true scope of theinvention, as defined by the appended claims.

I claim:

1'. A switch mechanism comprising, a rotatable threaded shaft, athreaded switch carrier threadedly engaged with a threaded portion ofsaid shaft so that upon rotation of the shaft the switch carrier ismoved longitudinally along said shaft, said switch carrier supportingtwo switches, stop means on the shaft on opposite sides of the switchcarrier, said switches having actuating arms in the path of said stopmeans so that as the switch carrier is moved longitudinally of the shaftthe two actuating arms are moved to actuate the switches as they eithercontact or separate from the stop means.

2. A switch means as defined by claim 1 characterized by, said'stopmeans being spiral springs of the same pitch as the threaded portion ofthe shaft and threadedly engaged with said shaft to be adjustable formovement along the shaft to vary the space interval between the stopsand therefore the operating interval of the two switches.

13. A control means for controlling the rotation of a shaft according toclaim it characterized by, said step means being spiral springs. of thesame pitch as the threaded portion of the shaft and threadedly engagedwith said shaft t'o be adjustable for movement along the shaft to varythe space interval between the stops and therefore the operatinginterval of the two switches, the threaded portion of said threadedswitch carrier being rotatable on the shaft relative to the switchcarrier in order to move the switch carrier longitudinally of the shaftto insure proper engagement of the switch actuating arms with said stopmeans. 7

4. A switch mechanism comprising, a rotatable threaded shaft, a motordriving said shaft to cause it to rotate, a threaded switch carrierthreadedly engaged with a threaded portion of said shaft so that uponrotation of the shaft the switch carrier is moved longitudinally alongsaid shaft. 7

5. A control mechanism comprising, a rotatable threaded shaft, athreaded carrier threadedly engaged with a threaded portion of saidshaft so that upon rotation of the shaft the carrier is movedlongitudinally along said shaft, said carrier supporting two controldevices, stop means on the shaft on opposite sides of the carrier,

said control devices each having actuating means in the 1 path of saidstop means so that as the carrier is moved longitudinally of the shaftthe actuating means are moved to actuate the control devices as theactuating means either contact or separate from the stop means.

References Cited by the Examiner UNITED STATES PATENTS 2,253,557 8/41Collins 20047 2,566,824 9/51 Carlson 2O047 2,600,568 6/52 Nelson318--468 X 2,951,920 9/60 Miller 200-47 ROBERT K. SCHAEFER, ActingPrimary Examiner.

OR'IS L. RADER, Examiner.

1. A SWITCH MECHANISM COMPRISING, A ROTATABLE THREADED SHAFT, A THREADEDSWITCH CARRIER THREADEDLY ENGAGED WITH A THREADED PORTION OF SAID SHAFTSO THAT UPON ROTATION OF THE SHAFT THE SWITCH CARRIER IS MOVEDLONGITUDINALLY ALONG SAID SHAFT, SAID SWITCH CARRIER SUPPORTING TWOSWITCHES, STOP MEANS ON THE SHAFT ON OPPOSITE SIDES OF THE SWITCHCARRIER, SAID SWITCHES HAVING ACTUATING ARMS IN THE PATH OF SAID STOPMEANS SO THAT AS THE SWITCH CARRIER IS MOVED LONGITUDINALLY OF THE SHAFTTHE TWO ACTUATING ARMS ARE MOVED TO ACTUATE THE SWITCHES AS THEY EITHERCONTACT OR SEPARATE FROM THE STOP MEANS.